Application of HEC-RAS 2D Model to Simulate Scour Depth Around Bridge Piers-A Case Study on Kelanisiri Bridge, Sri Lanka

Scouring refers to the lowering of the level of river bed due to water erosion. Formation of vortices in the vicinity of bridges due to obstruction caused to river flow by piers and abutments is the core rationale behind this pursuit. Precise scour depth prediction allows for cost-effective proactive measures, preventing more disruptive actions required when addressing advanced stage scour related issues. Within the scope of this study, a two-dimensional numerical model is developed using the HEC-RAS software for the determination of scour depth around the bridge piers of Kelanisiri bridge. Change in bed elevation around the bridge pier provides the depth of scour hole formed due to a considered flood event. A scour depth of 3.8m and 4.3m were obtained around the two piers of Kelanisiri bridge. Results of the simulation were validated with observed data and model performance was analyzed using statistical parameters. As per the results, two-dimensional hydraulic model coupled with the sediment transport model produced a reliable estimation of the river bed level change and the scour depth around the bridge piers. Further validation of the model results can be accomplished based on a series of laboratory-scale experiments.